The present invention relates, in general, to a wind power plant, and more particularly to a wind power installation of a type having a generator disposed in a nacelle and including a cooling circuit, and a turbine with at least one rotor blade.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
Typically, a wind power plant has a rotor blade which is rotatable around a horizontal axis and pivotable around a vertical axis to turn the rotor blade in appropriate alignment to the wind. The rotor blade is rotated by wind velocity at speed depending on diameter and shape of the rotor blade and its pitch to drive a generator, so that wind power is converted into electric energy. The conversion of energy normally results in energy loss in the form of heat. This heat loss applies in both the conversion of kinetic energy of wind into electric energy in the generator of a wind power plant as well for the electrical feeding of energy, generated by the wind power plant, into an electric power supply network. This heat loss takes place also in other electrical components, in particular the electronic power equipments, such as e.g. inverter or transformer. Also other components of the wind power plant heat up such as gears, bearings or control units like, e.g., hydraulic systems or similar control and regulation units, which adjust the rotor blades or turn the wind power plant towards the wind.
The heat loss amounts hereby to 5 to 7% of the installed nominal output. Heretofore, the heat loss has been dissipated into the environment by using fans which pull in cold air from outside to cool the corresponding component, e.g., the generator. The heated air is then discharged again to the outside. This is disadvantageous especially when the outside air is humid or has a high salt content particularly in coastal regions, and the components to be cooled are then exposed to this humid and salty air.
German patent publication no. DE 198 02 574 A1 describes a wind power installation having a generator which is cooled by an air stream produced by low pressure at a mouth of a rotor blade. This low pressure results in a pressure drop between each mouth of a rotor blade and an opening on a rotor blade distal side of the nacelle. As a consequence, ambient air is drawn in at the opening in opposition to the actual wind direction and flows via the flow path through the nacelle and through the interior of a rotor blade toward the mouth of this rotor blade. The provision of such a closed circulating ventilation is disadvantageous and, especially when located off-shore, results air with high salt content being aspirated. Moreover, noise is generated by the mouths at the rotor blades.
German patent publication no. DE 199 47 915 A1 describes a cooling system for cooling heat-generating structures in particular of a wind power plant, using a chimney effect of heated air to cool the structures in the foot region of the tower and also in a top area of the nacelle. It is hereby disadvantageous that the tower cross section is already formed with channels. Moreover, also a closed circulating ventilation system is involved here which is susceptible to penetration of dirt and humidity and thus is unsuitable for carrying out a reliable operation.
U.S. patent publication no. 2001/0035651 describes a wind power generating device in which lost energy of the generator is dissipated to the ambient air by direct heat conduction to the outer skin of the nacelle which is provided with ribs for surface enlargement. This cooling system is however able to dissipate only little heat energy.
It would therefore be desirable and advantageous to provide an improved wind power installation which obviates prior art shortcomings and is reliable in operation even for off-shore operation, without experiencing breakdown or maintenance works as a result of contaminated or salty cooling air.